What does escriban mean?

Escriban means 'they write.' It is the present plural form of the infinitive verb 'escribir' which means 'to write.'

You could say 'Ellos escriban' (for a group of men, or a group of men and women who write), 'Ellas escriban' (for a group of women who write), or 'Ustedes escriban' (when you are speaking directly to a group of people who write.)